1. The field of this invention is granular detergent compositions comprising phosphate builders, particularly sodium tripolyphosphate (STPP) and tetrasodium pyrophosphate (TSPP).
2. Phosphate built granular detergent compositions per se are known. The term "crutched" as used herein includes the usual subsequent step in which the material is "spray dried", unless otherwise specified. U.S. Pat. Nos. 4,165,334, Gosselink/Richmond/Wentler, issued Aug. 21, 1979; and 3,862,058, Nirschl/Gloss, issued Jan. 21, 1975, disclose detergent granular compositions comprising sodium tripolyphosphate (STPP) and disclose alkali metal pyrophosphates as suitable inorganic builders.
U.S. Pat. No. 4,019,998, Benson/Cherney/Collier, issued Apr. 26, 1977, discloses a pyrophosphate-silicate spray dried detergent with admixed glassy phosphate and less than 20% of alkali metal tripolyphosphate. This patent does not disclose any example of crutched and admixed STPP and TSPP.
U.S. Pat. No. 4,715,979, Moore/Evans/Hansen, issued Dec. 29, 1987, discloses an improved dissolving spray dried detergent with "little or no" (0-20%) pyrophosphate or anhydrous tripolyphosphate. This spray dried detergent is admixed with 0-300% of other builders and compacted and, optionally, admixed with 0-300% additional builders, etc. A pouched product is disclosed. No crutched, spray dried STPP/TSPP examples are disclosed.
U.S. Pat. No. 4,299,717, Cottrell et al., issued Nov. 10, 1981, discloses powder and bar sodium carbonate detergent compositions with a low level (1-12%) of pyrophosphate, other phosphates being below 5% by weight of the composition. The pyrophosphate may be spray dried or "post dosed to the composition." No example containing crutched and admixed STPP and TSPP is disclosed.
EPA 229,671 (Kao Corporation), published July 22, 1987, discloses a high-density (0.5 g/cc+) granular detergent with spray dried and admixed inorganic salts for flowability and solubility. No example of crutched (spray dried) and admixed STPP and/or TSPP is disclosed.
The problem with the prior art detergent granules which contain only a crutched (spray dried) or only an admixed phosphate builder system is that they suffer from inferior solubility.